Lasers, lamps, and other sources of electromagnetic radiation, particularly in the optical wavebands, are being increasingly utilized for various dermatological treatments and, in particular, for the removal of unwanted hair, spider veins, leg veins, other veins or other blood vessels which are visible through the patient's skin, lesions, port-wine stains, tattoos, and the like. In performing such treatments, it is desirable that the cost for the treatment be kept as low as possible, consistent with achieving desired results, and that risk of injury to the patient be minimized.
Since continuous wave (CW) lasers and other CW radiation sources are typically substantially less expensive than pulsed sources of comparable wavelength and energy, for cost reasons, it would be preferable to use CW sources rather than pulsed sources for such dermatological treatments. However, in order to avoid injury to the patient, the duration of energy application to a given area of the patient's skin must be controlled, this generally resulting in the more expensive pulsed light sources being used for the various dermatological treatments.
Further, since the only way to get radiation to areas where treatment is desired, which areas are normally in the dermis, is to transmit the radiation to such area through the overlying epidermis, some portion of incident radiation is absorbed in the epidermis creating the potential for damage thereto. This is a particular problem where melanin is being targeted in the dermis, as is for example the case for various hair removal treatments, since there is a substantial concentration of melanin in the lower portion of the epidermis at the dermal/epidermal (DE) junction. Further, the deeper in the dermis that treatment is desired, and/or the larger the element being treated, the more energy must be used, this generally involving the use of a more powerful laser or other radiation source and/or operating such source for longer time durations. This further increases the potential for epidermal damage.
Some attempts have been made in the past to scan a CW radiation source, such as the laser, over a treatment area, which has been done with the radiation source spaced from the skin in order to facilitate movement of the source. However, techniques currently utilized for protecting the epidermis frequently involve contact cooling of the epidermis and, for certain treatments such as hair removal, performing the treatment with pressure applied to the patient's skin is also desirable. Irradiation by use of a head in contact with the skin also permits more efficient transfer of energy into the patient's skin, thereby reducing the size of the source required for a given treatment energy density and, therefore, reducing the cost of such source. This cost could be further reduced if the radiation source is not the only source being utilized to heat the area under treatment.
Another problem in performing laser dermatology treatments, particularly when such treatment is to be performed over an area larger than the optical aperture of the applicator being utilized, is to obtain substantially uniform irradiation over the area so that sufficient radiation is applied to all portions of the area to achieve the desired treatment, while no portion of the area has so much radiation applied thereto as to cause thermal damage to the skin. Such uniform irradiation is very difficult with a pulsed source which typically utilize a circular aperture. Typically, the procedure followed is to irradiate a spot with a given pulse and to then reposition the head to an adjacent spot for irradiation. If the spots do not overlap, there will be portions of the area under treatment which do not receive radiation and, unfortunately, the radiation output is frequently not uniform over the entire optical aperture, being greater near the center, and less at the edges. Therefore, there is generally some overlap between adjacent spots. However, this results in some portions of the area under treatment receiving at least a double dose of radiation, which poses a potential danger of thermal damage in these overlap areas. Substantially uniform irradiation of a treatment area is therefore virtually impossible with a pulsed radiation source utilizing existing techniques.
Another problem which increases the energy required from the radiation source utilized is that, for existing systems, heating of the target to achieve the desired therapeutic effect is accomplished solely by radiation from the radiation source. If the temperature of the target could be increased by some type of preheating of the target volume, the amount of energy required from the radiation source to complete the job would be substantially reduced. However, such preheating must be achieved in a way such that the cost of such preheating is not greater than the savings achieved by reduced requirements on the radiation source.
Similarly, in order to protect the epidermis, many procedures require that the epidermis be cooled, preferably to the DE junction, to at least a selected temperature, for example 10° C., 0° C., or even slightly lower, before radiation is applied. If contact cooling starts when the head is over the target area, this means that there is some delay, perhaps half a second to a second, between the time the head is applied to the patient's skin and the time the radiation source is fired. With CW, such a delay once the radiation source is over the target area is difficult to achieve and it is therefore preferable that precooling of the epidermis occur for the target area before the radiation source is thereover. An ideal procedure would be to preheat the skin down to the target depth and then to precool to the DE junction, leaving the target depth preheated. Mechanisms in general, and heads in particular, for achieving such precooling and/or preheating followed by precooling have not heretofore existed.
It is also desirable to be able to focus the optical radiation at substantially the target depth. While heads have heretofore existed which are capable of achieving such a focus on a given spot, faster operation, particularly when operating in CW mode, although also when operating in pulse mode under some circumstances, can be achieved if there is a line focus at the target depth rather than a point focus. Mechanisms for achieving such a line focus have also not heretofore existed.
A need therefore exists for improved apparatus for utilizing optical radiation to treat various dermatological conditions, and in particular, improved heads for use in such apparatus which facilitate preheating and/or precooling of the target area, particularly when operating in CW mode, but also when operating in other modes, and which also facilitate achieving of a line focus for the radiation at a selected target depth for enhanced, and in particular, more rapid treatment.